Reactogenicity, immunogenicity, and antibody persistence in adults given inactivated influenza virus vaccines - 1978.

Monovalent A/USSR/77 (H1N1) and trivalent A/USSR/77, A/Texas/77 (H3N2), and B/Hong Kong/72 influenza virus vaccines from four manufacturers were tested in 292 adult volunteers. Systemic reactions were mild and resembled those with 1976 (swine) vaccines containing similar doses (in micrograms) of viral hemagglutinin. Trivalent vaccines caused more local inflammation than did monovalent, especially in older women. Two doses containing 7 micrograms of hemagglutinin each were required to induce a titer of hemagglutinin-inhibiting antibody of greater than or equal to 40 against A/USSR/77 virus in a majority of persons with an initial titer of less than 10, but one dose containing 20 micrograms of hemagglutinin did so; even one dose containing 7 micrograms was sufficient if the initial titer was greater than or equal to 10. Vaccine-induced titers of antibody to A/USSR/77 virus fell more during the six months after vaccination in younger than in older adults; this observation suggested that prior experience with related influenza viruses alters both production and persistence of antibody after vaccination. Seroconversions to A/Texas/77 and B/Hong Kong/72 viruses were more frequent in younger than in older adults with titers less than or equal to 20 before vaccination, but the final proportion of volunteers with titers of greater than or equal to 40 was high in both groups. Standardization of dosages in terms of micrograms of hemagglutinin appeared to reduce differences in responses to vaccines of different types and sources.